* Added support for passing collections to/from RNA functions,
this is done using a ListBase of CollectionPointerLink, which
is a standard ListBase link + PointerRNA.
* Added editable active uv/vcol layer to Mesh.
* Armature.bones now includes all bones, not only the ones without
parents.
* Modifier UV layer fields now are allowed to be empty, previously
this would set the name during modifier evaluation if there was
none.